1. Field of the Invention
This invention relates to a hot tap apparatus for insertion of a controllable device, in particular, a "pig" or robot, into an in-service pipeline, such as a gas distribution pipeline. More specifically, this invention relates to an apparatus for inserting and guiding electromechanical robots into pressurized piping systems, particularly, high-pressure systems. The apparatus of this invention can be used to sense the presence and the relative location of each robot inserted into the system as well as providing for robot storage, communication and recharging.
2. Description of Prior Art
Electromechanical "pigs", or robots, are used for internal inspection and repair of underground pipelines, thereby reducing the amount of labor required to detect damage to and repair of such underground pipelines by conventional means. However, in order to use such robots, it is necessary to be able to insert them into the pipeline and maneuver them within the pipeline without interrupting flow through the pipeline. Numerous apparatuses for hot tapping in-service pipelines for insertion of control valves, regulators, and flow stoppers are known. See, for example, U.S. Pat. Nos. 4,527,586, 4,240,459, 3,385,314, 2,396,964, 940,356, 3,652,107, 4,664,419, 3,108,499, and 587,107, all of which disclose various hot tap devices for installing a valve on a pipeline while the pipeline is operating under pressure. Such a device is also taught by U.S. Pat. No. 4,655,480 which teaches a molded tapping member for connecting a branch line to a pipeline having a U-shaped saddle piece with a shell shaped bight section and a pair of laterally spaced legs, each extending outwardly from an opposite end of the bight section. After positioning on the pipeline, current is applied to a heating wire mat incorporated into the U-shaped saddle piece for welding the tapping member to the pipeline. However, none of these references addresses the insertion of an electromechanical robot into an in-service pipeline.
To insert a robot into an in-service pipeline without interrupting the fluid flow through said pipeline, it is necessary to cut an opening in the pipe through which the robot can be inserted. To prevent fluid within the pipe from escaping, the opening is enclosed by a hot tap saddle sealingly secured to the pipe. The saddle is provided with a gate valve or other means for providing access to the pipe without permitting fluid to escape from the pipe. To make the necessary hole in the in-service pipe, it is known to use mechanical cutters, such as drills. Once the opening has been cut into the in-service pipe, the robot can be inserted into the pipe. However, it is important to remember that all of these operations must be carried out, including insertion and removal of the robot from the pipe, under conditions which prevent fluid from escaping from the pipeline as well as without interrupting fluid flow through the pipeline.
U.S. Pat. No. 4,334,806 teaches a capsule injection system for injecting capsules or carriers into a hydraulic pipeline system. The capsule injection system has a reservoir filled with a carrier liquid and a magazine rack mounted within the reservoir for holding capsules in series, one above another, for injection into the pipeline. The magazine holds the capsules, which are generally cylindrical, with their longitudinal axis generally parallel to the axis of the pipeline. Because the reservoir is open to atmospheric pressure, the liquid level within the reservoir must remain at a height which is a function of the gauge pressure contained within the pipeline. Thus, the reservoir must be relatively deep to accommodate high pressures.
U.S. Pat. Nos. 524,006 and 555,079 teach dispatch tube systems. The '006 patent teaches a branch tube having an external mechanical mechanism used to open and lower a gate within the branch tube, the gate closing off the piping system when inserting the carrier. The '079 patent teaches a device having an external mechanical mechanism for inserting a carrier from a branch line to a main line.
U.S. Pat. Nos. 3,139,932 and 3,866,628 teach devices for inserting well head tools into a well in which a tool diverter apparatus is installed at the junction of a Y which is automatically positioned to close one branch of the Y by a tool entering the well through the other branch of the Y.
U.S. Pat. Nos. 398,836 and 567,654 teach switches for pneumatic tubes which allow a carrier to be deflected from one tube into a branch tube. The '836 patent teaches an electrically actuated switch while the '654 patent teach a mechanically actuated switch. U.S. Pat. No. 3,206,140 also teaches a pneumatic carrier system for directing a carrier from one conduit to another conduit while U.S. Pat. No. 3,384,421 discloses a conduit shunting device for closing off one branch of a conduit.
U.S. Pat. Nos. 3,681,191, 4,264,244, and 3,826,539 teach diverter valves employing the principles of a turntable device. U.S. Pat. No. 3,868,071 teaches a flexible coupling which is used as a line selector for directing carriers within pneumatic tube systems.
U.S. Pat. Nos. 3,603,264, 3,508,497, and 4,826,360 generally teach closed transportation systems in which a carrier device or vehicle is moved from one point to another within the system. In particular, the '264 patent teaches a tube inspecting vehicle, the '497 patent teaches an underground high-speed transportation system, and the '360 patent teaches a transfer system for a transferring device within a clean room.